1. Field of the Invention
The present invention relates to a catalytic distillation process for the alkylation of organic aromatic compounds with olefins over an acidic catalytic distillation structure. More particularly the invention relates to an improvement in the process whereby the olefin concentration in the liquid phase is increased by increasing the olefin partial pressure in the vapor phase while maintaining a constant olefin feed rate and benzene to olefin ratio.
2. Related Art
Alkylation of organic aromatic compounds using catalytic distillation has been disclosed in U.S. Pat. No. 4,849,569 issued to Lawrence A. Smith, Jr. As practiced the process disclosed therein is embodied by two separate columns connected by liquid and vapor flow lines with one column being filled with a bed of the catalytic distillation structure and the second containing standard distillation structure. The olefin is fed below the catalyst bed, usually into the top of the second column. The aromatic compound is fed with the reflux into the top of the first column above the catalyst bed.
Theoretically the two columns should act as one continuous column. Increasing the olefin concentration in the vapor will increase the equilibrium olefin concentration in the liquid phase and thus the driving force for the reaction; resulting in a more economical process. However, the effect on the projected catalyst life may be deleterious as it has been found that a key variable in catalyst aging is the concentration of the olefin in the liquid phase in contact with the catalyst. Another associated effect is a decrease in the liquid benzene loading throughout the system which detrimentally affects the reaction kinetics and selectivities due to the reduction in the critical benzene to olefin ratio.